Method of producing printing-plates.



A. VALENTIN & J. ZBRREISS. METHOD or TRoDUcING PRINTING PLATES.

APPLIOATION FILED AUG. 16. 1909.

Patented Dc. 26, l1911.

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` or relating to AUGUSTE -Unrrnn sirnrns -rArENT OFFICE.

ULENTIN, or 1 Ucl` Ux, Vnim or coUnisnvoIE, METHOD oF -PnonUcINGPRINTING-PLATES.

lvpeciati f Letters fuient. Patented Dec. 26, l1911.

,/ Appucatiqpm'eg-August 1e; 190s. serial 513,072.

Toill whomi'itumwy concem:

f e it known that we, AUGUSTE VALENTIN,

a citizen ofthe Republic of France, `residing at Puteaux, Seine, France,and- ZER- Rnrss, a subject .of the German Empli'e, residing atCourb.evoie,Seine, France, have 1nvented certain: vnew :and usefulImprovements' inl Methods fof- Producing` Printing- Plates, ofwhichthevfollowing is a specifica- 13 uw,

61011. '1 "www w1: t

This inventinlrelates to-fimprovements V1n theproduction of printingplates. p I

In theI accompanying drawings 'Figures 1 to 9 illustrate the productionof screens and-x FfigsalO tolli illustrate-the 'manner in which aprinting plate is'etch'ed The process Y hereinafter 'described makes Aitpossible to' obtain direct 1 on metal `1. Plates engraved in intaglio lfrompositlve photographic line or half-tone originals.

, These'plates engraved in intaglio, reproduce, without any touching up,all the fine tones and all the half-tones of the positive originalprint. All the tones are constituted` by hollows the dimensions ofwhich, as regards extension and depth, are in exact proportion to thedifferent intensities .of tones.'

' It is a process which from the point of 'view of quality, has a doubleeiiiciency. An eiliciency produced by an extension of thehol'- `l0ws inproportionv to the intensity. of the tones, and an eliiciency producedby thel thickness of ink retained in the hollows, the depth of which isin proportion to diferillio -t e tenslty ofthe tones. The inking platesobtainedv by this process, can be efected simply by the use of an inking'and wiping .system which enables the -ink re quired for the printing tobe regulated acengraved relief for typographieprinting from v negativephotographic line or halftone originals. i v

General description of the process for obtaining plates 'engraved z'nintaglio- A thin copper plate, wellplanedvand polished on one of itssurfaces, is prepared, and on the whole surface of the said plate isspread a layer of the following solution: water 500 gr., b ichromate 'ofammonia 12 gr., sugar" 8 gr., gum arabic 110 gr., ammonia 9.9 drops.rlhe late covered with that solution is secure to a 'revolving supportwhich :is first operated slowly and "which is manipulated uniformlydistributed. Platesv above a gas` heating stove; giving oif a gentleheat which assists the drying. As soon as it is dried and cooled,theplate thus prepared I is ready .for beingppro'vided with a screen.

Thel screen is produced on `the whole surface of theplatephotographically, by using as the original 'a net-work arranged in apeculiar manner, as will be -hereinafter described, andhaving one of theshapes vshown in Figs. 4, 6 and -7 according to the nature of thepositive original to be engraved.v The pro'-A ceeding for thepurpose isas follows: The glass (orlilm) provided with'a screen,.is placed 'on theglass of a screw'printing press, withthe face providedfwith thescreen,.in-A ward.` The 4copper plate "prepared, as already' stated,- isplaced inrcontact with the screen. A thorough contactA between thescreen'andth'e' plate is insured by the screws of the printing frame,which are tightened as much aspossibled vThe whole is exposedto theaction of the sun, and when the action vor;

is considered sufficient, i the development is Y effected under Waterlfrom a' tap. The'plate suitably developed, lwill have on the whole ofits surface the image of the screeny constituted by a series of elementsproduced by the bichromate ysolution having been vrendered insolubleeverywhere where the light acted, that is to say, under the transparentelements of the screen. These elementsare V equal to each other, andtheir geometrical sus centers are at the same distance from each other.As will be seen farther on, the degree of exposure must be calculated soas to give `to the elements of the layer, a vsuilicient reslstanceto theaction of a mordantduring a certain time. They. must afterward crackwhen the action of the vmordant continues beyond .that time. As soon asthe metal plate provided with the screen is developed, it is coveredwith the following solution: water`360 gr., beer 100 gr., bi-chromate ofpotash 15 gr., citrate of iron 1.3 gr., sugar 1 gr., albumen 120 gr.,glycerin 2 gr., nitrate 100 of silver 5 gr. 4 The above must be -mi-xedand 125 gr. of flshglue. added to it.

The above solution is kept at. a tempera-` ture of about l17"' It isspread o n the whole surface 'of the plate on the revolving 105 support,and as soon as it isl dry, it is ready to receive the photographic imageto be engraved. Thev image., is reproduced photographically in 'theprinting frame. The

prepared surface of the pbite is placedinto the 'metal which Willbe'hollowed out, akind continuing,

The corrosive action the Walls of the said cup Will be corroded, and theelements of the screen of the first layer reduced. Theperchloridwill'pass afterward through `the tones of an intensity immediately belowthe strong shades, 'and successively through all the tones in proportionto their degree Vof eX- ofv cup being formed.

. posure. The action of the mordant will be 6 5'quired for forming theimage, being Aso to tion, the shape of the stopped by washing with Wateras soon as it begins to attack the strong lights of the subject. At thatmoment, the portions cor-` responding to the shades, will be constitutedby the elements of the screen reduced by corrosion to the state ofgranulated points owing to the cracking of the first layer (produced bythe long action of the mordant), and separated by deep. hollovvs orrecesses, While the portions corresponding to the lights, will be formedby the elements of the screen separated by slight hollovvs of small.

extent. The actionof the mordant produces a black oxidation of themetal, which enables'v v the engraving 0 y The image will appear inblack proportionoperation to be followed.

ately as the second layer sion oretching plate, cleaned With inked andrinted.

For obtaining plates engraved in relief, for typographie printing, theprocess is the same as just described for making printing platesengraved in intaglio, but 1n that case negative .originalsare used. Onthe other hand, the cracking of the/elements of the screen during thevetching must be delayed and become apparent only in the strongest 'Thisdelay of the perchlorid passing through the attacks the metal. -Thecorrohaving been completed, the potash, is ready to be about by anincrease of-strength ofthe elements produced on the first layer. Thisadditional strength is obtained by a longer exposure of the screen andby a- Weak burning y of the first developed layer.

Mechanical ewamz'mzton of the process.-

`As will be readily understood from the explanati'ons of the foregoinggeneral descrip screen and the nature of the layer'. constituting thesama-play an mlportant part as regards the final result.

The constitution of the second layer res .those employed inl squaresrendered absolutely say invariably fixed in accordance with .a

.could be obtained in practice. ,The researches of the applicants werechiefly 'directed, with regard to the said second layer, to the chemicalcom osition of the sensitive solution by means o which it'is possible toobtain, practically andin a thoroughly industrial manner, engravingsWhich-can be compared in; every respect to those produced by the layerof bi-chromated gelatin used in heliographic processes. The modificationof the final result in accordance with the nature of the subjects andthe nature of the negative or can therefore, Vbe generally produced onlyby the modification of the shapeofthe screen, of the nature of thescreen layer and the density of the mordantused.,forengraving Thesevarious elements will fbe examined and in conclusion the result 6" theirvariations in the different cases ofD their use vwill be given.

Preparation of glass, without' any grooves and perfectly flat, is takenand With the methods usually Wet collodion or any other The glass thusprepared and rendered sensitive, is arranged asusual in the frame of aphotographic apparatus provided with a screen-holder into which isplaced a screen with check pattern, similar in every Way to similarprocess.

apparatus in accordancewith the methods generally used inphoto-engraving, so as to produce, by exposure and o`n thedevelop-4ment, on the Whole of the surface of the sensitive glass a check shownin Fig. 1, that pattern of the shape is to say, formed by opaque by anenergetic intensification. Y These points are in contact with each otherat the corners and are very sharply defined at the side of thetransparent squares which separate them. The glass is covered Withrubber, covered with collodion and rendered sensitive. It is thenlreplaced in the frame ex-l actly at the point Where it` was at the rstexposure in the chamber. Exposure is again made by s uitablyarrangingthe screen and using for the exposure alarger opening in the lensdiaphragm than was used for the first exposure thereby producingslightly on the whole surface newly rendered sensitive, shaded oft' ordegraded points of the shape indicated in Fig. '2. The glass beingduring the second exposure exactly at the same place as itwasjduringithe first ex osure and it being of course understood t at thescreen is also located precisely at the same place during the secondexposure,pthe

positive originals employed,

screena-jA very good v then again.

prepared in accordance employed in the the mechanical engrav- .ingprocesses. The Whole is placedin the said degradation or shading oifwill be ef- Fig. 5, a glass is 'occurring in practice,

`plete reproduction of half-tones,

fected at the transparent` portions' of the first screen, and completedat the center of the same portions in a point rendered transparent by asuitable reduction. The screen, obtained by the combination of the twosuperposed images produced by the two lay ers differently exposed,l asjust described, will have the appearance shown in Fig. 3. Thev nalscreen required for the following operations, will be obtained byproducing from the screen thus made, a photographic counter-type whichatv the development'will present successivelytransparent, shaded-olf p1'degraded and opaque elements shown in Fig. 4.

Possible modifications of the nature of screens foon their 'use n thedifferent practical cases.-In the foregoingv examination of thepreparation of screens, the simplest method of proceeding for obtainingnormal screens, that is .to say, screens which are adapted to theconditions most frequently has been given. In certain cases where it isdesiredto h ave a high degree of ine'ness, as well as a comit will beadvisable to make other types of screens which, being more complete thanthose first described, will make it possible to produce on the firstlayer of the metal plate, a greater sensitiveness to the action of themordant. Thus the screen previously 'described is again covered with asolution of rubber rendered sensitive, and exposed as before, replacingthe round opening in the diaphragm by a square opening so as to obtainsquare points on the third sensitive layer of the plate, after asuitable exposure and development; .the geometrical centers ofthe squarepoints will coincide with the geometric centers .of the round pointsformed on the first and on the second layer, and the screen will appearwith three series of points of diiferent intensity and of differentshape uniformly superposed Aon each other on the whole surface of theplate.

For making a screen of the form shown in ner with moist collodion or anyother sensitive emulsion, and the glass thus sensitized is placed in theframe of the photograhpio apparatus, the network screen being arrangedin front of the glass at a suitable distance, whereupon a rounddiaphragm with a small opening is placed into the object glass, and o nthe pattern plate of :the apparatusv is placed a strongly. lighted whitepaper. vThe sensitized plate is-exposed by uncovering the object glassfor about 2 minutes, the glass thus exposed isdeveloped, and there willappear round opaque points. The developed glass is fixed, washed anddried thenafter having been lcovered with a weak solution of rubsprepared inv thek usual maii-v on the whole surface ber is again coveredwith collodion and sensitized, then replaced intothe frame of thephotographic' apparatus in order to be again ex osed behind the networkscreen than duringthe irst exposure), 'a roun dia hragm with a largeropening being use After a suitable exposure, there will appear, afterthe development, on surface of the glass round points superposed overthe first one and of a larger surface, and a network'screen will thus bereduced, provided on the whole of itssur ac'e with fine opaque roundpoints or `in the center of other roundpointsmore more transparent, thatwith two gradations. This screen having been produced thus the plate isagain covere with a solution of rubber, with collodion and sensitized,then exposed in the chamber behind the network screen arranged asbefore, a square diaphragm being used for this exposure in order, afterthe development, to produce, on the whole surface of the plate,.squarepoints touching each other with their corners, and

widely dispersed and is to say a screen (care being taken to move it allttlesfarther away the whole l dots arranged the operation iscontinued, the sensitive layers being superposed and secured to eachother by said layers show successively as above described: The rst, fineopaque round points obtained by using a round diaphragm with a smallopening. The second, round points more widely dispersed and less opaquethan the rst ones, and obtained by using a round diaphragm with a largeropening.` The third, square points touching .each other with theircorners and` less. opaque than 1the preceding ones, obtained by using asquare diaphragm. The.. fourth, square points touchingeachother well attheir corners,

and leaving between them transparent square points with rounded olfcorners, and obtained by using a square diaphragm with recessed corners.The fifth, points, the angles of which penetrate decidedly into eachother, and which leave between themround transparent points, this formof dots being obtained by the use of a square diaphragm theangles ofwhich are recessed considerably. The superposition of these different.

forms of screens on one and the same glass, will form the screen shownin Fig.

' As is well known, the points produced on a sensitized glass through anet -work screen, vary in shape and in distance from each otheraccording to the shape of the diaphragm used, and: the distance of thenetwork from the sensitive glass; it will thus be understood thatJ itwill. be easy to vary to .an infinite extent the -forms of networkscreens, superposed in the manner described on one and the same glass.hand, it is 'possible to. givevto each of the superposed sensitizedlayers, diferentdethe weak solution of rubber. The

On the other n grees of opacity by reducing Vthe intensity after thedevelopment by means ofa solution of cyanid of iodin. Thus for thescreens shown in Figs. 6 and 7 round diaphragms will be used, theopenings of said diaphragms increasing with each of the sensitive layersplaced on the same' glass, the

said layers being suitably treatedl after the development to producelfinally a gradation lof intensity of the different forms of points thatwill have been superposed.

- It will' be evident that the screens can be constructed so as to givea larger area to the transparent elements as shown in Fig. 6, or

e sure of the screen,

,on the contrary, so as to .give .a larger area .1. Square elementsdistinctly transparent, and 2. Elements opaque at their geometricalcenters, the opacity decreasing from' the centers to the circumference.When a screen is produced on the first layer by the expothere Will beproduced on the whole surface of the plate a positive image of thescreen, that is to say, there will be formed on the said surface squareelementsdistinctly opaque and square elements transparent at theirgeometrical centers and decreasing in transparency from their center totheir circumference the said decrease being however only slight, lsothat nally there will be a great difference between the opaque squaresand the adjoining ones. It is necessary to take another factor intoaccount, in the formation of the screen, to witz-the opposition Abetweenthe Atransparentsquares and the opaque squares of the screenbeing verygreat, the limit marking the difference ofexposure, will followdistinctly a line only provided that theA thickness of the sensitivelayer is zero. But in reality that is not the case, and there will Vbeformed a well known irridiation phenomenon (Figs. 8 and 9). v

In Fig. 8,. g is the screen, ethe thickness of the first layer and Z thesource of light. Fig. 9 is plan of Fig. 8. A slight additional exposure,outside the periphery of the opaque square will reinforce the square onthe'lwhole of its circumference following the outline n, and the platewill show after the development and drying, a screen layer which willhave different degrees of exposure which will be4 equally repeated onthe whole of its surface, at each geometrical center of the points whichdivide it'up. A. copper plate provided with a screen, will, therefore,be formed, which Vcan be .by the will present, if submitted to theaction' of a mordant, a very great sensitiveness and will be capable ofundergoing that action with a very special precision. Thissensitivenessgraphically illustrated by Figs. 10 and 11. y

In Fig.' 10, e represents the first. layer, the different thicknesses ofe representthe different degrees of exposure. l The dotted linesindicate the action of the accordance with the different degrees ofexposure.

etching in Fig. 11 is a plan of Fig. 10, which shows l the differentdegrees of resistance to the action of the acid, due to the differentdegrees of exposure. Thus, the portion M will offer the main'mumresistance for a certain time, after which it will crack. The portion Nwill have a resistance between the resistances M and P. '-The portion Pwill have a resistance decreasing from N to' Q. lThe portion Q will haveno resistance and will b e attacked as soon as the mordanthas passedthrough the second layer. If, -011 the other hand, the distance R,separating the geometrical centers of the resisting points of the layer,is varied by the use of different sus sizes of screen, it will be seenthat if R increases, between spreadsl and reduces the number of portionssensitive to the action of the mordant`; while, on the contrary, if Rdecreases, the number of sensitive-portions increases. At the/limit,that is to say, when R becomes inthe scale ofl existing sensitivenessinitely small, there willA be obtained .on the metal plate a layerhaving such a constitution that each of its points will present acomplete sensitiveness lto all the tones, and the action of the mordant,regulated sensitiveness of the said layer, will produce on the metalplate an engraving which will reproduce, by its different recesses, allthe fine-tones and tones of the subject. I

Preparation of the .second Zagen-As soon as the plate providedwithlascreen, has been developed and dried, it is covered w1th volvingsupport. As soon as it is dried, it is exposed under the positive printor original of the image to be engraved, and after a suitable exposurewhich varles 1n accordance with the subjects, it is ready to beengraved.

Engraving.-For the constitution of the two adjoining geometricalcenters' all the half- Athe second layer which is put on on the refirstlayer practice has shown the vuse' of a screen of the shape shown inFig. 4;

1 g2g Aa solution of the following formula:

water 500 gr., bichromate 'of ammonia 12 gr., gum arabic 110, sugarSgr., and ammonia 9.9 drops, to be suitable. In these conditions, theetching is effected normally by the use of a' solutionof perchlorid ofiron of 45 B. in the following manner :l

resented by the diagram of Fig. 12, the'dif-i ferentthicknesses of whichrepresent the intensities of the tones, that isto say, the portion 6represents the transparent por- .tions of the: original (the lights)Athe portions 5, 4, 3,2 the tonesof increasing intensity up to theportion 1 which represents the opaque portions. The perchlorid will passfirst through the portions of the second layer which have been exposedthe least, that is to say, the portions 1 correspending to the deepshades and will attack that is to say,f1n the center o of the points q,r, s, t (Fig.= 11) which will be hollowed out and will spread as vtheetching is con- 20 cessively through the portions 2, 3, 4, 5 and 6 andwill successively hollow out the cen.

lv.`v The action of etching will continue to spread toward theperiphery, and the hollow will assume the Ashape indicated by o. Theetching continuing, the angles g, 7', s, t of the resisting 'points ofthe layer, will intersect each other, and the hollows cor'- respondingto the tone 3, will spread to y. The hollows corresponding to the tone2,

will spread out to m, the hollows correspond' ing to thetone 1 will bevery widely spread and will leave between them only a wea point.Moreover, the etching in these portions having been prolongeehthe' firstlayer will crack, and the perchlorid, passing through the said layer,will granulate the surface of the points, and the finished plate i willhave the appearance shown in Fig. 12. Special conditions determz'nmg,the 'use of thediferent shapes of screens, the nature of the #rst layerand .the density of' the m07*- dam to be used-Photographic printsrequired for producing engraved plates generally have 'differentcharacteristics as regards their photographic qualities. The saiddifferent qualities will be defined with reference to three types oforiginals or printsldened in the following manner:

lst type. The difference of intensity between the lights andthe shadesis normal, that'is to sa'y,the lights are transparent, and the shadesstrong Without opacity.4 The details are well defined. The original orprint is good. 1 2nd xtype. The difference ofl intensity between thelights and shades is slight, that is v to say,

thejmetal 'everywhere where it is exposedv tinued. The perchlorid willthen pass suc-l 'ond type).

the lights are not absolutely transparent, and the shades notvery'strong, the details being deined. The print is gray.

3rd type. The difference of intensity between the lights and the shadesis strong, 7 0 that is to say, the pure lights are transparent,

-the shades are opaque and the details are generally faintly'drawn. Theprint is hard.

In order to determine the variations to which must be subjected each ofthe three elementsl Whic can be usefully modified (shape of the screen,kind of the first layer, density ofthe mordant) in the differentpractical cases, let 'us examine first what will happen when the natureof the said 30 three elements .is normal, that is to say, such as itought to be for obtaining a good result when a print of the first typeis used.

In that case experience has shown that: the screen mustbe of the shapeshown in Fig. 4; the first layer is given by the followingformula1`water 500` gr., bichromate ofammonia '12 gr., gum larabic 110gr., sugar 8 gr., and ammonia 9.9 drops; the density of thev mordant(liquid perchlord of iron) 40o B. These elements having thus beenexperimentally determined, let the result of using them with the threetypes of print described be considered. Assuming that.

for the purpose three copper plates are provided with a screen of theshape shown in Fig. 4, with a first layer of the normal formula, and allthree comprising a second sensitive layer of the same formula.v

Figs. 12-14 show the action of the etch 100 ing on the three copperplates provided in the inann'er described with a screen of the formshown in. Fig. 4. These three plates comprise layers of the same kind,ybut they are exposed each under 'a different positive. 105

k' Fig. 12 shows the actionof etching on one of the said plates exposedunder a positive which is good (first type). Fig. 14 shows the action ofetching on one of the saidv plates exposed under a gray positive (sec-Fig.` 13 shows the action of etching on one ofthe said plates exposedunder a hard positive (third type).

Figs. 12-14 comprise each three -Views connected by a brace. The upperlviews represent the tones of the positive, the different intensities ofwhich are represented by the different thicknesses. The portions 1represent the shades, and the portions 6 the lights. The center viewsare views in v plan of the engraved plates, the surfaces of the hollowsbeing shown by black portions. The bottom views are sections on 'theline A-A of the engraved plates. They indicate the depth of the hollowscorrespending to each of the 'tones andthegradationA of the etching.Letthe first of these plates (Fig. 12) be exposed under a positive oftherstr type,

.that is to say,

u nder a very good posit1ve; the second un- 130 der a positive of thesecond type (Fig. 14)

' and the third under a positive of the third type (Fig. 13). Let theetching be done will be thethird to then 1n a perchlorid .of 40 B. Bydividing up the action of the etching into three stages (first-stage:etching the shades; second stage; etchin half-tones; third stage:etching the lights, it will be seenthat in the first stage: vthe plateexposed under the hard positive will be first 'attacked in the shadeportion. The plate exposedunder the good original will be the second tobe attacked in the shade portion. The plate j' the half tones.' Theplate exposed under the hard print or original, will be ,the third to'be' attacked in the half-tones. In the third stage: the plate exposedunder the gray original or 'print will be the, first to bel attackedinthe light portion. The plate 'exposed under the good original or printwill be the second to be attacked in the,

light portions. The plate exposed under the hard original or print willbe the third to be attacked in the light portions. In short, the plateexposed under the gray original print will be the last to be 'attackedand the first toA be finished. The action of the mordant is, therefore,exercised for a very short time; the

shades will not have had time to be suiiciently hollowed out, and thepoints will not be suliicien'tly reduced. Ony the other' hand, thecracking of the rst la er will not take place, so that, onbeing ed in,the plate will have a regular or uniform appearance. Inorder tolincrease .the eiect, 1t would have been necessary that at the shadesthe points yshould have been more reduced, that y'is to say, that thesaid points should have been at the smaller and less resisting. Thiswould have been"insured b the use of a screen ofthe shape shown 1n Fig.7, and byfffthe use for the -iirst-,la e'r of' a solution of smallerresistance. n the other hand, it

1s wellvvknown that, when the4 density of the perchlorid is great, it'passes with greater and passes j th'rough it only in -the shadeportions and up to a certain degree of exposure. .It will, therefore, bepossible to utilize this property which, by the use of a perchlorid ofsuitable density will enable the shades to be`hollowed `outbeforeattacking the half-tones and a suicient hollow and reduction of thepoints to be obtained.'

When thesaid result is reached in the shade portion, the etching will becontinued by beginning of the etching' Athrough the second layer,

substituting for the perchlorid of'high den'- sity, a perchlorid osmaller density which will pass through the half-tones and hollow outthe metal at the same time reducing the points. As regardsthe lights,the density of the perchlorid will be still further de- Icreased, and aplate engraved by gradation will be roduced, which gradatlon willincrease t e effect by doing away with the yuniformity of the etching.For facilitatrst ing'the cracking of the layer in the shade portion, asolution of smaller resist` ance will be used for forming the saidlayer.

Similar considerations deduced from the preceding observations, wouldlead to show that when a hard print is usedrit is necesand thedensities. of the mordants to be used for each of the three types ofprints previously described, could be defined as follows:

Normal-orzgz'nal .or pmtt. -First layer: Screen of the shape shown inFig. 4 (transparent elements equal to opaque elements). Solution of thefollowing formula: 500 gr. of water, 12 gr. of bichromate of ammonia,100 gr. of gum arabic, 6 gr. of sugar and 9.9 drops of ammonia. Etching.First stage: solution of perchlorid of iron of 40 B. Second stage:solution of perchlorid of iron of '38 B. Third stage: solution ofperchlorid of iron of- 35 B.

Gray original or 'pmi- First layer:

Screen of the shape shown in Fig. 7 (transparent elements smaller thanthe opaque elements). Solution ofthe following formula: 509 gr. ofwater, 12 gr. `of bichromate of ammonia, 110 gr. of gum arabic, 8 gr. ofsugar, and 9.9 dro s of ammonia. Etching. First stage: solution ofperchlorid of iron of B. Second stage: solutifvp of perchloridof iron of40' B. Third` stage: solution of perchlorid of iron-of 38 B.

Hard vowgz'nal .or print-First layer: A

screen ofthe form shown in Fig. 6 (transparent elements larger lthan theopaque elements). Solution of the following formula: water v500 gr.,ibichromate of ammonia'12 gr., gum arabic .135 grl, su ar 10 gr., andammonia 9.9 drops. vEtc ing. First stage:

solution of perchlorid of iron of 38 B. Secr ond stage: solution ofperchlorid Vof iron of 34.6 B. Third stage: solution of-perchlorid ironof 34 B. f

General. applications of the procesa-It is `possible by means of thisprocess to producev engraving' plates -for printing in several colors,whethertheoriginal single color `prints have been obtained by .any ofthereproduction processes at present used, or

whether they have been obtained bythe processes of photographicselection lfrom nature 45 the second ditto in plate ditto or fromoriginals in colors. It is, however, necessary to distinguish moreparticularly one of the most important applications' which makes itpossible to produce from otDucos du Hauron,

- other words,'it will photographic color originals or prints obtainedfrom nature bythe Lumiere processes print, three single-color printingplatesA (-yellow, red and blue) engraved direct in 1ntaglio, which onbeingprinted by the present process and registered onl one and the samevehicle (paper, fabrics, etc.,') will re-v produce all the colors of thepositiveoriginal or print used. For obtaining this result, it will benecessary to prepare three copper tplat-es which will be provided withan iden- .tical screen in the manner described, on a first layerof thesame formula. The iirst of these plates will be covered with a secondlayer orthochromatized for the yellow. The

second of these plates will be covered with a second layerorthochromatized for the red. Thethird of the .said plates will becovered with a second layer orthochromatized for the (yellow, red vandblue) will reproduce withblue. The first plate will be exposed under theoriginal polychromatic print by arranging a violet screen on ing frame.The second plate.' will be exposed under the original polychromaticprint by arranging on'the glass of the rinting frame a green screen.vThe third p ate will be exposed under the original polychromatic .printby arranging on the glass of the printing frame an orange screen. Inthat way, exposed, the second layer on the plates being on each of thesaid plates will be'rendered insoluble,yin proportion to the intensityof the yellow, red and blue radiations, and on engraving thel'e will beobtained 0n the first plate single colorreproduction in yellow, onredand on the third in blue. The' superposed impressions ofthe saidthree engraved plates out anyx touching up, thezexact` image of the'color print or original used. In this kind of engraving and colorprinting the same perfection willbe obtained as in engraving andprinting in black. It will also be possible to obtain from single-coloror polychromatic originals black'or color printing plates of a subjectin anyrsize byI applyingethe method of photographic projection 'to thef`present process.,

'We claim 1. The method of producing printing plates, which consists' incovering the metal plate with a sensitivelayer, then exposing thesamerunder a screen so as to produce on.

vthe whole surface of the lplate square ele'- it forms a the glass ofthe printla-yer .to dry so that it forms a said plate the image lto 'beammonia, exposing ments distinctly', opaque and elements transparentv attheir geometrical centers which elements decrease in'transparency fromthe center to the circumference, then developing the said plate,covering the plate with a sensitive layer, allowing the said layer todry so that it forms a ilm, vthen producing onsaid layer the image to beengraved by means of an exposure through an ordinary photographicoriginal or print, and then subjecting the plate thus exposedto theaction of a mordant.

2.The method of producing plates, which consists in covering the metalplate with a sensitive layer, exposing the same-under a screen so as toproduce on the whole surface of the plate square elements distinctlyopaque and elements transparent at their eometrical centers whichelements decreasev 1n transparencyl from the center to thecircumference, then developing the said plate, covering the, plate witha sensitive layer, allowing the said layer to dry so that film, thenproduc' g onsaid layer the image to be engraved y means 'of an exposurethrough an ordinary photographic original or print, and then subjectingthe plate thus exposed to the action of a mordant consisting ofperchlorid of iron having a density varying' between 34 and 45 degreesB. according to the intensity of the p otographic original or printused.

'3. The method of `producing printing plates, which consists in coveringthe metal plate with a`sen'sitive layer comprising bichromate ofammonia, sugar and gumprinting l arabic, exposing the same under ascreen so as to produce on the whole surface of the plate squareelements distinctly opaque and elements transparent at their geometricalcenters which elementsy decrease in transparency from the center tothecircumference, then .developing the plate, covering the late with asensitive layer comprising blchromate of potash, citrate of iron sugarand nitrate of silver, allowin the said then producing on engraved bymeans of an exposure through an ordinary photographic original or print,and then subjecting the plate to the action of a mordant.

l 4:. The methodof producing rintin plates, which consists in. coveringt e meta Aplate with a layer consisting of suitable proportionsof.water,-bi.chromate of ammonia, sugar, gum arabic and a few drops Vofthe same under a screen soas -to produce on the whole surface of theplate square elements distinctly elements transparent at theirgeometrical centers which elements decrease in transthus exposed opaqueand parency from lthe center to the circumfer- .f

" suitable prop ortions of water, beer, bi-

lthel image to be engraved by means of an exposure through an ordinaryphotographic original or print, and then subjecting the' plate thusexposed to the action of a mordant. v

5. Th method' of producing prin plates; which consists in covering themeta plate with a layer consisting of suitable proportions of water,bi-chromate of ammonia,

mon1a5 exposing the same under a screen so as' to produce on the wholesurface of-the plate square elements distinctly opaque and elements.transparent at their geometrical centers which elements decrease intransparency from the center to the circumfen' ence, th en developingthe said plate in Water,

covering the plate 'with a layer consisting of the image to be engravedby means of an exposure through an ordinary photographie original or4print, and then subjecting the plate thus exposed to the action of amordant consisting of perchlorid of iron having a density varyingbetween 34 and 45 degrees o B.' according to the intensity of the photolgraphic original or print used. sugar, gum arabic and a few drops of amvIn testimony whereof We have aiixed our signatures, in presence of twosubscribing witnesses..

- AUGUSTE VALENTIN. JEAN ZERREISS. Witnesses: l

JUL1N CAECRN, H. C. CoxE.

